1. Field of Invention
The present invention relates to a chainless planetary transmission for a pedal-powered vehicle such as a two passenger tricycle taxi.
2. Description of the Prior Art
The conventional three speed bicycle drive is characterized by a pedal and crank assembly which rotates a pedal sprocket to drive a chain for rotating a rear sprocket coupled to the wheel hub. The rear sprocket drives a planetary gear system inside the wheel hub. The pedal sprocket is typically three times larger than the rear sprocket, and a planetary gear system typically multiplies the sprocket ratio by 3/4 for first gear, by 1.0 for second gear and by 4/3 for third gear.
The chain for the conventional three-speed drive requires periodic cleaning and oiling for efficient operation and must be removed to change the rear tire. Cleaning is particularly necessary in dusty areas to prevent hard pedaling and premature chain failure.
The chainless drive systems of the prior art are either impractical, excessively complex, or costly to manufacture and maintain. U.S. Pat. No. 2,505,464 entitled "Bicycle or Motorcycle Carrying A Single Steering Wheel and Transmission Gears and Connections Therefor", issued Apr. 25, 1950 to L. Debuit, is typical of one form of chainless drive. The drive is located on the driving wheel axis and concentric with the pedal shaft axis, but the transmission is not of the planetary type, and it is located outside the wheel hub. In addition, torque from the pedal drive shaft is transmitted through single gear teeth which require heavy gears to prevent early fatigue failure of the gear teeth.